It has been proposed to power nose and/or main aircraft landing gear wheels with electric and other drive motors to drive aircraft autonomously or independently during ground travel and move aircraft without operating the aircraft main engines to provide thrust or using tow vehicles. The airline industry, moreover, is beginning to acknowledge that continuing to use an aircraft's main engines to move aircraft during ground operations is no longer the best option and is associated with safety issues, excess fuel use, and other challenges that may pose significant concerns for airlines. Improvements in aircraft ground travel that avoid reliance on aircraft main engines for motive power, including the use of landing gear wheel-mounted electric and other drive motors to power aircraft ground movement, continue to be sought. Control of the actuation of and transfer of the torque required to drive powered aircraft landing gear drive wheels, for example, must ensure that these drive wheels are driven only in a desired direction or only during selected times and conditions when an aircraft is driven autonomously during ground travel and that wheel drive systems are not engaged or operational at other times.
Many types of vehicle torque transferring clutch assemblies are known in the art. U.S. Pat. No. 3,075,623 to Lund; U.S. Pat. No. 3,599,767 to Soderquist; and U.S. Pat. No. 7,661,329 to Cali et al., for example, describe clutch assemblies incorporating sprag or pawl elements that may transmit torque between races or rotatable elements depending, in part, on their relative directions of rotation. One way vehicle clutches designed to lock in one direction and allow free rotation in the opposite direction are also available, as are improved selectable one way clutch designs, such as those described in U.S. Pat. No. 6,290,044 to Burgman et al.; U.S. Pat. No. 7,980,371 to Joki; and U.S. Pat. No. 8,042,670 to Bartos et al. Various other selectable clutch designs that provide controllable overrunning and coupling functions in automotive automatic transmissions, are described in U.S. Pat. No. 8,079,453 to Kimes and in U.S. Patent Application Publication Nos. US2010/0252384 to Eisengruber; US2011/0233026 to Pawley; and US2013/0277164 to Prout et al. While the foregoing clutch designs may function effectively to transfer torque in automotive applications, including in powered vehicle drive wheels, they are not sufficiently robust to withstand loads on aircraft landing gear structures during landing and to function effectively and reliably in an aircraft landing gear wheel drive system environment. Moreover, these systems do not provide the kind of failsafe capability that ensures that the clutch will never be engageable during flight, landing, takeoff, or during any other aircraft operating condition when operation of an aircraft landing gear wheel drive system would be unsafe.
A range of aircraft landing gear wheel drive systems that may be used to drive aircraft on the ground without reliance on aircraft main engines has been proposed in the art. U.S. Pat. No. 7,445,178 to McCoskey et al.; U.S. Pat. No. 8,109,463 to Cox et al.; U.S. Pat. No. 8,684,300 to Wilson et al.; and U.S. Patent Application Publication Nos. 2009/0294577 to Roques et al.; 2010/0065678 to Kiyosawa; and 2010/0276535 to Charuel et al. are illustrative of various drive systems intended to move aircraft autonomously on the ground. U.S. Pat. No. 7,469,858 to Edelson; U.S. Pat. No. 7,891,609 to Cox; U.S. Pat. No. 7,975,960 to Cox; and U.S. Pat. No. 8,109,463 to Cox et al., owned in common with the present invention, describe aircraft drive systems that use electric drive motors to power aircraft wheels and move an aircraft on the ground without reliance on aircraft main engines or external vehicles. While the drive motors described in the foregoing patents and published applications may be used to move an aircraft autonomously during ground operations, it is not suggested that torque transfer between the drive motors and the aircraft landing gear wheels driven by the drive motors may be achieved by selective activation of a powered clutch assembly or system that reliably and selectively transfers torque to an powered aircraft drive wheel only when safe operation of the aircraft wheel drive system may be ensured.
A need exists, therefore, for a reliable clutch assembly with the advantages of a selectable one—way clutch that is specifically designed to be an integral component of an aircraft powered landing gear wheel drive system and to selectively and safely transfer torque only when required to drive an aircraft drive wheel and move the aircraft autonomously on the ground and, further, that has a failsafe mechanism activatable to ensure that the powered clutch assembly may not engage the aircraft drive wheel to transfer torque unless the powered landing gear wheel drive system may be operated safely.